Dental materials

ABSTRACT

The invention relates to compositions containing:
         (a) 14 to 55 wt.-% fillers,   (b) 3 to 35 wt.-% of at least one mono- or polyethylenically unsaturated compound which is not a urethane (meth)acrylate,   (c) 0.1 to 5 wt.-% of at least one initiator system which is capable of starting a radical reaction,   (d) 1 to 40 wt.-% plasticizers,   (e) 0 to 10 wt.-% auxiliaries such as dyes, pigments, stabilizers, solvents, rheological additives such as flow-improvers and/or retarders, and   (f) 30 to 81.9 wt.-% of at least two urethane (meth)acrylates with different molecular weights, these being present in a molecular weight ratio of 1.5:1 to 50:1.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/EPOO/12774 which has an Internationalfiling date of Dec. 15, 2000, which designated the United States ofAmerica.

The present invention relates to compositions for the preparation ofdental materials with improved mechanical properties and the use of suchdental materials, in particular as provisional or temporary crowns,bridges, fillings, inlays and onlays.

In the case of the preparation of provisional or temporary crowns,bridges, inlays and onlays, low-viscosity to viscoplastic materialsbased on ethylenically unsaturated compounds are involved, depending onthe use, which can be provided with organic and/or inorganic fillers andcured by polymerization (called “provisional K+B materials” hereafter).

Two different classes of provisional K+B materials are current: on theone hand so-called polymethyl methacrylate materials (PMMA materials)and on the other hand so-called composite materials.

The PMMA materials consist of a powder/liquid system the powderessentially being a PMMA powder with dyes and initiator constituents andthe liquid consisting mainly of methyl methacrylate and/or iso-butylmethacrylate and also initiators and stabilizers.

Crowns and bridges prepared from PMMA material are characterized by alow fracture susceptibility and good elastic properties. A decideddisadvantage of these materials is however that they are irreversiblydeformed if a load is placed on them.

Thus with PMMA materials, material is provided which is less fractureprone, but however easily permanently deformable, which becomes unusablefor the patient if too great a load is placed on it. In additionmaterials based on PMMA are physiologically questionable as they containtoxic acrylate systems.

The composite materials normally consist of paste/paste systems whichcan be either manually admixed or present in a double-chamberedcartridge and are admixed by means of a dispenser and a static mixingdevice, as described in EP-A-0 232 733 and EP-A-0 261 466. In the caseof the monomers used in this material class, mainly difunctionalethylenically unsaturated compounds are involved which, when curing,effect a high cross-linking level of the resulting polymer matrix. Glasspowder, silica gels and quartzes are essentially used as fillers.

Through the high cross-linking level and the hard fillers, hard andbrittle materials are obtained which do not flow under a great load, butfracture.

With composite materials therefore, a material is provided which is verydimensionally stable, but however fracture prone, which likewise becomesunusable for the patient if too great a load is placed on it.

From the state of the art, urethane (meth)acrylates, essentially7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-dioxy-dimethacrylate(UDMA, for example Plex 666-1, Röhm, Darmstadt) have also been describedas monomers for composite materials.

By acrylates or (meth)acrylates are meant in general acrylates and/ormethacrylates within the framework of this document.

UDMA slightly improves the fracture susceptibility, however compositesprepared with UDMA are still always brittle materials which are fractureprone in particular in thin areas or when used in bridges.

In order to further reduce fracture susceptibility, differentunsuccessful attempts have been carried out:

-   -   The incorporation of polymers which, due to the marked swelling        behaviour in the monomer matrix, leads to a marked increase in        viscosity.    -   The use of plasticizers which is accompanied by a marked decline        in mechanical properties such as the compression and bending        strength as well as the release of harmful substances into        bodily fluids.    -   The use of high-molecular, low-functional monomers, such as        polyethylene glycol diacrylate which improves the fracture        susceptibility, but greatly reduces the mechanical properties        and also leads to a marked increase in temperature during curing        and is therefore not usable for application in the mouth.

In summary, none of the methods known to date leads to a usableimprovement of the fracture susceptibility and dimensional stability ofprovisional composite-based K+B materials.

DE 198 41 205 A describes light-curing resin materials for orthodonticswhich, in addition to fillers, initiator systems and plasticizers,contain (meth)acrylates containing urethane bonds with a molecularweight of 300 to 5,000 g/mol and at least one unsaturated double bond,mixtures of such compounds of different molecular weight not being ruledout, as well as in addition (meth)acrylates free of urethane bonds withan average molecular weight of 100 to 300 g/mol and at least oneunsaturated double bond. In relation to the previously named compounds,it is stated in the description in lines 12 to 14 of page 3, that themolecular weight may not exceed 300 as otherwise the obtained curedmaterial is brittle and is unsuitably defective in terms of durability.

WO 99/40884 describes dental materials based on polymerizable acrylicmonomers, polymerization initiators and inhibitors as well as fillers.Compositions which contain urethane (meth)acrylates with differentmolecular weights as well as unsaturated compounds which have nourethane (meth)acrylate, are not disclosed here. The compositionsdescribed in the examples contain an single urethane methacrylate.

The object of the invention is to provide a composite-based dentalmaterial which has a reduced fracture susceptibility with simultaneouslyhigh dimensional stability.

This object is achieved by compositions containing:

-   -   (a) 14 to 60 wt.-%, preferably 20 to 50 wt.-% fillers,    -   (b) 3 to 35 wt.-%, preferably 5 to 25 wt.-% of at least one        mono- or polyethylenically unsaturated compound which is not a        urethane (meth)acrylate, and has a molecular weight between 300        and 5,000 g/mol,    -   (c) 0.1 to 5 wt.-%, preferably 0.1 to 4 wt.-% of at least one        initiator system which is capable of starting a radical        reaction,    -   (d) 1 to 40 wt.-%, preferably 2 to 30 wt.-% plasticizers,    -   (e) 0 to 10 wt.-%, preferably 0.000001 to 8 wt.-% auxiliaries        such as dyes, pigments, stabilizers, solvents, rheological        additives such as flow-improvers and/or retarders, and    -   (f) 30 to 81.9 wt.-%, preferably 35 to 73 wt.-% of at least two        urethane (meth)acrylates with different molecular weights, these        being present in a molecular weight ratio of 1.5:1 to 50:1 and        the higher molecular urethane (meth)acrylate having a molecular        weight between 1,000 and 20,000 g/mol and the lower molecular        urethane (meth)acrylate a molecular weight between 300 and 1,000        g/mol.

The materials according to the invention are suitable in particular foruse in the preparation of provisional or temporary crowns, bridges,fillings, inlays and onlays.

It was surprisingly found that materials prepared from the compositionsaccording to the invention display a much-improved fracturesusceptibility with simultaneously high dimensional stability. Thematerials according to the invention have improved elastic propertieswith extensive retention of mechanical stability.

The terms “comprising” or “containing” are always intended to introducea non-limitative list within the framework of this document.

The fact that the word “a” is used before naming a feature does notexclude the possibility that the named features can be present manytimes, in the sense of “at least one”.

Component (a) comprises customary fillers for dental materials, forexample glass and quartz powder, silica gels, pyrogenic highly-dispersedsilicic acids, insoluble plastics, low soluble fluorides, as describedin U.S. Pat. No. 5,824,720, as well as mixtures of these components.These fillers can be X-ray opaque through suitable additives, such asfor example barium or strontium-containing glasses or also throughcompounds such as YF₃. Pyrogenic highly-dispersed silicic acids aresuitable for example as fillers influencing thixotropy. Furthermoresoluble organic polymerisates, such as polyvinyl acetate as well as itscopolymers can also be added in such a quantity that the viscosity ofthe pastes allows them to be used in cartridge systems customary in thetrade, as described in EP-A-0 232 733 and EP-A-0 261 466.

Cristobalite, calcium silicate, zirconium silicate, molecular sievessuch as sodium aluminium silicate, metal oxide powder such as aluminiumor zinc oxide or their mixed oxides, barium sulphate, yttrium fluoride,calcium carbonate, plaster and plastic powder are for example alsosuitable as fillers.

The named fillers can be hydrophobized for example by a treatment withorganosilanes or -siloxanes or by the etherification of hydroxyl groupsto alkoxy groups.

It has been shown that the use of purely organic, insoluble fillers isnot suitable to achieve the present object, as aesthetically low-gradedental materials with unsatisfactory physical values are obtained.

Component (b) is an at least mono- or polyethylenically unsaturatedcompound which is not a urethane (meth)acrylate and preferably has aviscosity smaller than 5 Pa·s at 23° C. (cone/plate viscometer).Compounds with a different viscosity are also suitable however. Thecompounds have a molecular weight between 300 g/mol and 5,000 g/mol,particularly preferably between 300 g/mol and 1,000 g/mol.

Acrylic acid esters and/or methacrylic acid esters of an ethoxylatedand/or propoxylated compound, of a polyether or of an alkylpolyol areparticularly suitable as component (b).

This can involve for example Di(meth)acrylates of alkyl compounds,preferably with 2 to 20 C atoms. Di(meth)acrylates of hexanediol (6 Catoms), octanediol (8 C atoms), nonanediol (9 C atoms), decanediol (10 Catoms) and eicosanediol (20 C atoms) are preferred.

Di(meth)acrylates of ethoxylated and/or propoxylated compounds, forexample of ethylene glycol, polyethylene glycols, polypropylene glycols,polyethylene-co-propylene glycols are also suitable.

Furthermore Di(meth)acrylates of ethoxylated Bisphenol A, for example2,2′-bis (4-(meth)acryloxy-tetraethoxyphenyl)propane are suitable.

As component (c), the compositions according to the invention contain atleast one initiator system which is suitable for generating radicals.Redox systems or radiation-curing systems or also mixtures of differentcatalyst systems are principally suitable.

For example, an initiator system consisting of an amine and a peroxidecomponent as described in DT-PS-97 50 72, can be a redox system. Thepolymerization is started here by the peroxide compound. A tertiaryamine is used for example as polymerization accelerator. A furthersuitable system is also described by Albert Groβ in “Quintessenz derZahntechnik [Essentials of Dentistry]”, 1977, 7, Report No. 293.Usually, the amine component is worked into a paste, the so-called basepaste. For the most part, this base paste also contains the monomersprovided for polymerization. The peroxide component is worked intoanother paste, the so-called catalyst paste. The spatial separation ofthe two initiator components is necessary to avoid a premature curing ofthe monomer proportions.

A similar initiator system for the polymerization of unsaturatedhydrocarbons is also described in DE-A-95 56 33, which contains heavymetals and also an amine and sulfonium component. Also named in EP-A-0374 824 is an initiator system with an organic peroxide compound and atertiary aromatic amine as activator (accelerator). For example, allthese systems can be used alone or in combination in the compositionsaccording to the invention.

The initiator systems have a more favourable temperature development andalso an improved colour stability which is described for example inDT-C-14 95 520. The composition from DT-C-14 95 520 polymerizes at lowtemperature in a short time and without using external energy. Thedescribed systems contain barbituric acid derivatives and/ormalonylsulfamides, ionogenically-bonded halogen and/or a heavy metalcompound and/or organic peroxides. EP-A-0 374 824 also describes such aninitiator system of barbituric acid derivative, peroxide, heavy metalcompound and ionogenic halogen.

Furthermore the polymerizable composition according to the invention cancontain a photoinitiator system. This can also be present in addition toat least one of the other initiator systems or as a single initiatorsystem. Suitable photoinitiators are for example the bisacylphosphineoxides described in U.S. Pat. No. 4,792,632 and U.S. Pat. No. 4,737,593.

It is essential for the invention that the initiator systems require nosupply of energy in the form of heat to produce radicals. Heat-curingsystems are unusable for use as dental materials, in particularmaterials which cure in the patient's mouth.

The polymerizable compositions according to the invention can containcustomary plasticizers, preferably with a viscosity smaller than 10 Pa·sat 23° C. (cone/plate viscometer), as component (d). These are forexample polyethylene glycol derivatives, polypropylene glycols,low-molecular polyesters, dibutyl, dioctyl, dinonyl, diphenyl phthalate,di(iso-nonyladipate), tricresyl phosphate, paraffin oils and siliconeoils.

Auxiliaries, such as dyes, pigments, stabilizers, solvents and/orrheological additives such as flow-improvers can be added as component(e).

Furthermore the vinyl compounds described in EP-A-0 374 824 as component(d) can be used for example as retarders to lengthen the setting times.

Component (f) consists of at least two urethane (meth)acrylates withdifferent molecular weights with a molecular weight ratio of 1.5:1 to50:1, preferably 1.5:1 to 20:1, particularly preferably 1.5:1 to 10:1and quite particularly preferably 1.5:1 to 5:1. It is particularlyadvantageous if, in the compositions according to the invention, theacrylates of this component constitute at least 50 wt.-%, preferably atleast 60 wt.-%, particularly preferably at least 70 wt.-% of the totalethylenically unsaturated compounds [(b)+(f)].

The higher molecular acrylates of this component have a molecular weightbetween 1,000 g/mol and 20,000 g/mol, preferably between 1,000 g/mol and15,000 g/mol and particularly preferably between 1,000 g/mol and 10,000g/mol.

The lower molecular acrylates of this component have a molecular weightbetween 300 g/mol and 1,000 g/mol.

The higher-molecular urethane (meth)acrylate of component (f) can be apolyester, polyether, polybutadiene and/or polycarbonate urethaneoligomer (meth)acrylate.

By polyether urethane oligomer (meth)acrylate is meant a compound forexample which contains at least polyether, urethane and (meth)acrylategroupings.

These urethane oligomer (meth)acrylates are accessible, in that apolyester, polyether, polybutadiene and/or polycarbonate diol (diolcomponent) with an aliphatic, cycloaliphatic and/or aromaticdiisocyanate, for example 1,6-hexamethylene diisocyanate (HDI),2,4,4-trimethylhexamethylene-1,6-diisocyanate (TMDI), tetramethylenediisocyanate, isophoron diisocyanate, 4,4′-dicyclohexylmethanediisocyanate, 1,4-phenylene diisocyanate, 2,6- and 2,4-toluenediisocyanate, 1,5-naphthylene diisocyanate, 2,4′- and4,4′-diphenylmethane diisocyanate (diisocyanate component) are reactedunder amine or tin catalysis (C. Hepburn, “Polyurethane Elastomers”,2^(nd) Ed. Elsevier Applied Science, London and New York, 1992). If amolar excess of diol component compared with diisocyanate component ishereby used, terminal OH groups remain which can be esterified with anethylenically unsaturated acid such as acrylic acid or methacrylic acidor one of their derivatives. If a molar excess of diisocyanate componentcompared with diol component is used, terminal isocyanate groups remainwhich are reacted with a hydroxyalkyl and/or hydroxyaryl (meth)acrylateand/or di(meth)acrylate and/or tri(meth)acrylate, such as for example2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate (HEMA),3-hydroxypropyl methacrylate (HPMA), 3-hydroxypropyl acrylate (HPA),glycerol dimethacrylate and/or glycerol diacrylate.

The preparation of the previously named urethane (meth)acrylates can beinferred from C. Hepburn, “Polyurethane Elastomers”, 2^(nd) Ed. ElsevierApplied Science, London and New York, 1992.

Usable polycarbonate polyols are for example products which result fromreaction with diols, such as 1,3-propanediol, 1,4-butanediol,1,6-hexanediol, diethylene glycol, neopentyl glycol,trimethyl-1,6-hexanediol, 3-methyl-1,5-pentanediol and/or tetraethyleneglycol, with diaryl carbonates such as diphenyl carbonate, or withphosgene, as described in U.S. Pat. No. 4,533,729, DE-A-169 40 80,DE-A-271 43 03 or EP-B-0 343 572.

Usable polyether polyols include for example products which areaccessible by polymerization of a cyclic oxide, for example ethyleneoxide, propylene oxide or tetrahydrofuran or by addition of one or moreof these oxides to polyfunctional initiators such as water, ethyleneglycol, propylene glycol, diethylene glycol, cyclohexane dimethanol,glycerol, trimethylol propane, pentaerythrite or Bisphenol A.Particularly suitable polyether polyols are polyoxypropylene diols andtriols, poly(oxyethylene-oxypropylene) diols and triols which areobtained by simultaneous or sequential addition of ethylene andpropylene oxide to suitable initiators, as well as polytetramethyleneether glycols, which result from polymerization of tetrahydrofuran.

Suitable polyether polyols can also be obtained for example under thename “Desmophen” from Bayer, Leverkusen.

The polyester polyols are reaction products of low-molecular polyolswith low-molecular polycarboxylic acids.

Low-molecular polyols or polyol mixtures suitable for this are forexample ethylene glycol, propylene glycol, 1,4-butanediol,1,6-hexanediol, diethylene glycol, triethylene glycol, neopentyl glycol,1,4-bis(hydroxymethyl)-cyclohexane, dipropylene glycol. Glycerol,trimethylol propane or pentaerythrite are suitable for example ashigher-functional polyols which can also be used proportionally, forexample from 0 to 20 wt.-%, to introduce branchings into the polyestermolecule. 1,6-hexane diol and neopentyl glycol are particularlysuitable.

The low-molecular polycarboxylic acids can be for example aliphatic,cycloaliphatic, aromatic and/or heterocyclic. Instead of the freepolycarboxylic acids, corresponding polycarboxylic acid anhydrides orpolycarboxylic acid esters with low alcohols can also be used. Asexamples, there can be named: succinic acid, adipinic acid, sebacinicacid, azelaic acid, phthalic acid, isophthalic acid, phthalic acidanhydride, tetrahydrophthalic acid anhydride, glutaric acid anhydride,maleic acid, maleic acid anhydride, fumaric acid, terephthalic aciddimethyl ester. Adipinic acid is particularly preferred.

Suitable polyester polyols can also be obtained for example under thename “Desmophen” (Bayer, Leverkusen).

Polyesters which are accessible for example by polymerization oflactones, such as caprolactone, in conjunction with a polyol, canlikewise be used. Polyester amide polyols can be obtained byproportional use of amino alcohols, such as ethanol amine, in thepolyester-formation mixture.

Suitable polyolefin polyols are for example butadiene homo- andcopolymers with terminal hydroxyl groups which can be obtained forexample from BF Goodrich Speciality Chemicals, Cleveland, Ohio.

Commercially available urethane (meth)acrylates with a molecular weightgreater than 1,200 g/mol are for example as follows, but the list doesnot claim to be complete and the invention is not to be understood aslimiting in any way:

Urethan-MA 92-456, Urethan-A 98-446, Genomer 4269, Genomer 4215, Genomer4246 (Rahn AG, Zurich), Ebecryl 230, Ebecryl 270, Ebecryl 930, (UCBChemicals, Kerpen), BR-304, BR-374, BR-3731, BR-582E, BR-7432, BR-204(Bomar Specialities Co., Winsted).

The urethane (meth)acrylate used according to the invention with thesmaller molecular weight of component (f) can be for example a reactionproduct from a difunctional, for example aliphatic, cycloaliphaticand/or aromatic isocyanate, such as 1,6-hexamethylene diisocyanate(HDI), 2,4,4-trimethylhexamethylene-1,6-diisocyanate (TMDI), butylisocyanate, tetramethylene diisocyanate, isophoron diisocyanate,4,4′-dicyclohexylmethane diisocyanate, 1,4-phenylene diisocyanate, 2,6-and 2,4-toluene diisocyanate, 1,5-naphthylene diisocyanate, 2,4′- and4,4′-diphenylmethane diisocyanate, under amine or tin catalysis with ahydroxyalkyl and/or hydroxyaryl (meth)acrylate and/or di(meth)acrylateand/or tri(meth)acrylate such as 2-hydroxyethyl acrylate (HEA),2-hydroxyethyl methacrylate (HEMA), 3-hydroxypropyl methacrylate (HPMA),3-hydroxypropyl acrylate (HPA), glycerol dimethacrylate and/or glyceroldiacrylate.

Usually, dental materials are formulated from the compositions accordingto the invention as two-component paste-paste systems in applicationsystems or devices, such as cartridges from Mixpack, Rotkreuz.

The volume ratio of the pastes can be in the range from 1:1 to 20:1,preferably 4:1 to 10:1. The quantitatively larger component is hereaftercalled base paste, the smaller catalyst paste. However, the componentscan also be present distributed over three or more pastes.Single-component formulations are also possible with suitable choice ofcatalyst system.

The base paste can contain the total quantity of components (b) and (f),in addition optionally parts of quantities of components (c) and (d).

The catalyst paste optionally contains the residual or all quantitiesand/or constituents of components (c) and (d).

Component (e) can be contained in the base or catalyst paste or alsodistributed over both pastes. Component (a) is contained in the basepaste or distributed over base and catalyst paste.

Mixing can be carried out by static or dynamic mixing processes. Manualadmixing of the components is also possible, the components being storedfor example in screw-top tubes or tubes, measured and mixed manually,for example by strand-length comparison.

A particularly preferred version within the framework of the inventionis dosage as a two-component system with static mixing element.

A further preferred version of the invention relates to a kit for thepreparation of a dental material containing either no or at least oneapplication apparatus for the application of dental materials, no or atleast one static mixing element, at least one cartridge with at leasttwo chambers which are filled with a composition according to theinvention.

The components are hereby distributed as follows for example:

-   -   Base paste: Component parts from (a), (b), parts from (c), parts        from (e), (f)    -   Catalyst paste: Component parts from (a), parts from (c), (d),        parts from (e).

Shaped bodies prepared according to the invention can have for example abending strength, measured according to the 4-point bending test, ofover 40 MPa, preferably from 70 to 150 MPa.

The fracture susceptibility of the shaped bodies according to theinvention is for example maximum 40% with an endurance test of 100,000loads of 100 N.

The invention is described in more detail in the following usingexamples, the invention not being limited in any way by the examples.

Preparation examples

100 g base and 10 g catalyst paste respectively are kneaded from theconstituents listed hereafter of the preparation examples 1 to 5. Someof this is filled in 10:1 cartridges from Mixpack, Rotkreuz. For use,they are pressed by means of a dispenser through a static mixing deviceand mixed. Curing takes place within a few minutes.

Compo- Quantity Quantity nent Base 1 g wt.-% Component Catalyst 1 gwt.-% a) Dental glass powder (Ø < 12 μm), silanized 25 25 a) Dentalglass powder (Ø < 12 μm) 3.4 34 with methacryloxypropyltrimethoxysilanea) Microfine silicic acid, silanized (HDKH 5 5 a) Microfine silicicacid, silanized (HDKH 0.7 7 2000, Wacker, Burghausen) 2000, Wacker,Burghausen) c) Bis-(1-phenylpentane-1,3-dionato)- 0.00775 0.00775 c)1-benzyl-5-phenyl barbituric acid 0.1 1 copper(II) c)(β-phenylethyl)-dibutyl-ammonium-chloride 0.352 0.352 c)3,5,5-trimethylhexanoic acid tertiary 0.06 0.6 butyl ester b)2,2-bis-4-(acryloxy-pentaethyleneglycol)- 13.77 13.77 d)2,2-bis-4-(2-hydroxyethoxyphenyl)- 5.74 57.4 phenylpropanepropane-bis-acetate f) Genomer 4215 (Rahn AG, Zurich) 6.89 6.89 f)Genomer 4205 (Rahn AG, Zurich 48.98025 48.98025

Compo- Quantity Quantity nent Base 2 g wt.-% Component Catalyst 1 gwt.-% a) Dental glass powder (Ø < 12 μm), silanized 25 25 a) Dentalglass powder (Ø < 12 μm) 3.4 34 with methacryloxypropyltrimethoxysilanea) Microfine silicic acid, silanized (HDKH 5 5 a) Microfine silicicacid, silanized (HDKH 0.7 7 2000, Wacker, Burghausen) 2000, Wacker,Burghausen) c) Bis-(1-phenylpentane-1,3-dionato)- 0.00775 0.00775 c)1-benzyl-5-phenyl barbituric acid 0.1 1 copper(II) c)(β-phenylethyl)-dibutyl-ammonium-chloride 0.352 0.352 c)3,5,5-trimethylhexanoic acid tertiary 0.06 0.6 butyl ester b) TEGDMA13.77 13.77 d) 2,2-bis-4-(2-hydroxyethoxyphenyl)- 5.74 57.4propane-bis-acetate f) U 98-446 (Rahn AG, Zurich) 13.77 13.77 f) Genomer4205 (Rahn AG, Zurich 42.10025 42.10025

Compo- Quantity Quantity nent Base 3 g wt.-% Component Catalyst 1 gwt.-% a) Dental glass powder (Ø < 12 μm), silanized 25 25 a) Dentalglass powder (Ø < 12 μm) 3.4 34 with methacryloxypropyltrimethoxysilanea) Microfine silicic acid, silanized (HDKH 5 5 a) Microfine silicicacid, silanized (HDKH 0.7 7 2000, Wacker, Burghausen) 2000, Wacker,Burghausen) c) Bis-(1-phenylpentane-1,3-dionato)- 0.00775 0.00775 c)1-benzyl-5-phenyl barbituric acid 0.1 1 copper(II) c)(β-phenylethyl)-dibutyl-ammonium-chloride 0.352 0.352 c)3,5,5-trimethylhexanoic acid tertiary 0.06 0.6 butyl ester b) TEGDMA10.33 10.33 d) 2,2-bis-4-(2-hydroxyethoxyphenyl)- 5.74 57.4propane-bis-acetate f) Ebecryl 230 (UCB, Kerpen) 10.33 10.33 f)7,7,9-trimethyl-4, 13-dioxo-3, 48.98025 48.98025 14-dioxa-5, 12-diazahexadecane-1, 16-dioxy- dimethacrylate

Compo- Quantity Quantity nent Base 4 g wt.-% Component Catalyst 1 gwt.-% a) Dental glass powder (Ø < 3 μm), silanized 25 25 a) Dental glasspowder (Ø < 12 μm) 3.4 34 with methacryloxypropyltrimethoxysilane a)Microfine silicic acid, silanized (HDKH 5 5 a) Microfine silicic acid,silanized (HDKH 0.7 7 2000, Wacker, Burghausen) 2000, Wacker,Burghausen) c) Bis-(1-phenylpentane-1,3-dionato)- 0.00775 0.00775 c)1-benzyl-5-phenyl barbituric acid 0.1 1 copper(II) c)(β-phenylethyl)-dibutyl-ammonium-chloride 0.352 0.352 c)3,5,5-trimethylhexanoic acid tertiary 0.06 0.6 butyl ester b)2,2-bis-4-(acryloxy-pentaethyleneglycol)- 13.77 13.77 d)2,2-bis-4-(2-hydroxyethoxyphenyl)- 5.74 57.4 phenylpropanepropane-bis-acetate f) U 98-446 (Rahn AG, Zurich) 6.89 6.89 f)7,7,9-trimethyl-4, 13-dioxo-3, 48.98025 48.98025 14-dioxa-5, 12-diazahexadecane-1, 16-dioxy- dimethacrylate

Compo- Quantity Quantity nent Base 5 g wt.-% Component Catalyst 1 gwt.-% a) Dental glass powder (Ø < 1 μm), silanized 25 25 a) Dental glasspowder (Ø < 1 μm) 3.4 34 with methacryloxypropyltrimethoxysilane a)Microfine silicic acid, silanized (HDKH 5 5 a) Microfine silicic acid,silanized (HDKH 0.7 7 2000, Wacker, Burghausen) 2000, Wacker,Burghausen) c) Bis-(1-phenylpentane-1,3-dionato)- 0.00775 0.00775 c)1-benzyl-5-phenyl barbituric acid 0.1 1 copper(II) c)(β-phenylethyl)-dibutyl-ammonium-chloride 0.352 0.352 c)3,5,5-trimethylhexanoic acid tertiary 0.06 0.6 butyl ester b)2,2-bis-4-(acryloxy-pentaethyleneglycol)- 13.77 13.77 d)2,2-bis-4-(2-hydroxyethoxyphenyl)- 5.74 57.4 phenylpropanepropane-bis-acetate f) Ebecryl 270 (UCB, Kerpen) 10.33 10.33 f)7,7,9-trimethyl-4, 13-dioxo-3, 45.54025 45.54025 14-dioxa-5, 12-diazahexadecane-1, 16-dioxy- dimethacrylate Ø: diameter

Testpieces with dimensions 4 mm*4 mm*35 mm were prepared and, in anendurance test, loaded 100,000 times with 100 N in water at 36° C. inthe 4-point bending test according to FIG. 1 (one load per second,support at a distance of 30 mm, load at a distance of 15 mm, maximumpossible deformation of the sample pieces of 1.4 mm determined by theapparatus).

The results obtained are summarized in the following table:

Bending strength Endurance test [MPa] 4-point bending 100,000 loadsDental material test of 100 N Comparative example 1: 40 100% of thetestpieces TRIM permanently deformed (Bosworth, Illinois) after lessthan 10,000 loads Comparative example 2: 70 100% of testpieces Flexspanbroken (Jeneric/Pentron, Wallingford) Comparative example 3: 85 75% oftestpieces Luxatemp Automix broken (DMG, Hamburg) Preparation example 160 25% of testpieces (according to the broken invention) Preparationexample 2 50 35% of testpieces (according to the broken invention)Preparation example 3 50 40% of testpieces (according to the brokeninvention) Preparation example 4 70 25% of testpieces (according to thebroken invention) Preparation example 5 60 30% of testpieces (accordingto the broken invention)

The dental materials according to the invention, according topreparation examples 1 to 5, show a clearly reduced fracturesusceptibility and/or improved dimensional stability vis-à-visconventional materials. The dental materials according to the inventionhave a bending strength sufficient for provisional K+B materials inaddition to low fracture susceptibility.

1. A composition comprising: (a) 15 to 60 wt.-% fillers, (b) 3 to 35wt.-% of at least one mono- or polyethylenically unsaturated compoundwhich is not a urethane (meth)acrylate and has a molecular weightbetween 300 and 5,000 g/mol, (c) 0.1 to 5 wt.-% of at least oneinitiator system which is capable of starting a radical reaction, (d) 1to 40 wt.-% plasticizers, (e) 0 to 10 wt.-% auxiliaries, and (f) 30 to81.9 wt.-% of at least two urethane (meth)acrylates with differentmolecular weights, a high molecular weight urethane (meth)acrylatehaving a molecular weight between 1,000 and 20,000 g/mol and a lowmolecular weight urethane (meth)acrylate having a molecular weightbetween 300 and 1,000 g/mol, being present in a molecular weight ratioof 1.5:1 to 50:1.
 2. The composition according to claim 1, in which theurethane (meth)acrylates of component (f) constitute at least 50 wt.-%of the total weight of the ethylenically unsaturated compounds (b) and(f).
 3. The composition according to claim 1 or 2, the high-molecularweight urethane (meth)acrylate being selected from the group consistingof polyether (meth)acrylates, polyester (meth)acrylates andpolycarbonate urethane oligomer (meth)acrylates.
 4. The compositionaccording to claim 1 or 2, component (b) being an acrylic acid esterand/or a methacrylic acid ester of at least one compound selected fromthe group consisting of an ethoxylated compound, a propoxylatedcompound, a polyether and an alkylpolyol.
 5. The composition accordingto claim 1 or 2, in which component (d) has a viscosity smaller than 10Pa·s at 23° C.
 6. The composition according to claim 1 or 2, in whichcomponent (d) has a molecular weight between 150 g/mol and 5,000 g/mol.7. The composition according to claim 1 or 2 that is in the form of asystem of at least two pastes able to be admixed in customary dentalapplication systems.
 8. The composition according to claim 1 or 2 thatis formulated as a single-component system.
 9. 10. A kit for thepreparation of a dental material, comprising at least one cartridge withat least two chambers which are filled with a composition according toclaim 1 or 2 and optionally comprising at least one apparatus forapplying a dental material and further optionally comprising at leastone static mixing element.
 11. A cured composition according to claim 1or
 2. 12. An apparatus comprising at least one cartridge containing acomposition according to claim 1 or
 2. 13. The composition of claim 1,in which the auxiliaries are at least one selected from the groupconsisting of dyes, pigments, stabilizers, solvents and rheologicaladditives.
 14. The composition of claim 13 in which the auxiliaries areat least one rheological additive that is a flow-improver or a flowretarder.
 15. A method for preparing a dental piece selected from thegroup consisting of a provisional crown, a dental bridge, a dentalfilling, a dental inlay and a dental onlay comprising forming thecomposition of claim 1 or 2 into the dental piece and curing thecomposition.
 16. A method for preparing a dental material with afracture susceptibility of maximum 40% in an endurance test of 100,000loads of 100 N comprising: i) providing a composition comprising (a) 15to 60 wt.-% fillers, (b) 3 to 35 wt.-% of at least one mono- orpolyethylenically unsaturated compound which is not a urethane(meth)acrylate and has a molecular weight between 300 and 5,000 g/mol,(c) 0.1 to 5 wt.-% of at least one initiator system which is capable ofstarting a radical reaction, (d) 1 to 40 wt.-% plasticizers, (e) 0 to 10wt.-% auxiliaries, and (f) 30 to 81.9 wt.-% of at least two urethane(meth)acrylates with different molecular weights, a high molecularweight urethane (meth)acrylate having a molecular weight between 1,000and 20,000 g/mol and a low molecular weight urethane (meth)acrylatehaving a molecular weight between 300 and 1,000 g/mole, being present ina molecular weight ratio of 1.5:1 to 50:1; and ii) curing thecomposition.
 17. The method of claim 16, in which the auxiliaries are atleast one selected from the group consisting of dyes, pigments,stabilizers, solvents and rheological additives.
 18. The method of claim17, in which the auxiliaries are at least one rheological additive thatis a flow-improver or a flow retarder.
 19. A method for preparing adental material with a bending strength, measured according to the4-point bending test, of over 40 MPa comprising: i) providing acomposition comprising (a) 15 to 60 wt.-% fillers, (b) 3 to 35 wt.-% ofat least one mono- or polyethylenically unsaturated compound which isnot a urethane (meth)acrylate and has a molecular weight between 300 and5,000 g/mol, (c) 0.1 to 5 wt.-% of at least one initiator system whichis capable of starting a radical reaction, (d) 1 to 40 wt.-%plasticizers, (e) 0 to 10 wt. -% auxiliaries, and (f) 30 to 81.9 wt.-%of at least two urethane (meth)acrylates with different molecularweights, a high molecular weight urethane (meth)acrylate having amolecular weight between 1,000 and 20,000 g/mol and a low molecularweight urethane (meth)acrylate having a molecular weight between 300 and1,000 g/mole, being present in a molecular weight ratio of 1.5:1 to50:1; and ii) curing the composition.
 20. The method of claim 19, inwhich the auxiliaries are at least one selected from the groupconsisting of dyes, pigments, stabilizers, solvents and rheologicaladditives.
 21. The method of claim 20, in which the auxiliaries are atleast one rheological additive that is a flow-improvers or flowretarder.